The present invention relates to exercise apparatus of the dynamometer type.
Exercise dynamometers are used in physical conditioning programs and in medical and scientific performance evaluations. A typical exercise dynamometer includes a work input element which can be manually moved by the person exercising on the apparatus. The work input element may include a set of pedals like those on a bicycle, a roller or belt which can be moved by running along surfaces, foot pads which can be moved by motion simulating skiing or stair climbing, hand cranks and the like. The work input element is linked to a motion element such as a flywheel, and some form of device for resisting movement of the motion element. For example, a simple bicycle type exercise dynamometer may have a flywheel, a set of pedals linked to the flywheel and a mechanical band brake for resisting rotation of the flywheel. The degree of resistance is set by adjusting the tension on the band, as by turning a screw to tighten a tension spring connected to the band.
U.S. Pat. No. 4,934,692 discloses a variant of this approach in which an electric motor is provided to adjust the band tension. The electric motor is controlled by a switch mounted on a hand crank used by the person performing the exercise, so that he or she can adjust the tension conveniently without interrupting the exercise U.S. Pat. No. 5,016,871 discloses another device including an electric motor for tightening and loosening a brake band. Devices relying on manual control, whether applied by direct manual adjustment of the brake band or by manual actuation of an electric motor adjustment, provide only the crudest control of the exercise program. Accordingly, considerable effort has been devoted towards development of exercise apparatus with automatically controlled resistance.
U.S. Pat. No. 4,998,725 discloses a controller for an exercise machine such as a treadmill or stationary cycle which uses a microprocessor to vary resistance to the exerciser to regulate the user's heart rate. To vary the resistance in the stationary cycle embodiment, a motor geared to a shaft winds or unwinds a tension strap provided for the flywheel.
U.S. Pat. No. 4,824,104 discloses isokenetic exercise apparatus which uses frictional braking to provide constant speed exercise. The rotational speed of an exercise member generated by the user is mechanically compared to that of an axle which is rotated at a constant speed. The difference between these two rotational speeds is then translated into linear axial movement to thereby further apply or partially release braking resistance.
In U.S. Pat. No. 4,709,917 resistance to a brake wheel is varied by a solenoid. An iron core within the solenoid is linked to a lever so that movement of the core adjusts the resistance of the mechanical brake.
Another approach is to use an electrically controllable element directly to resist the force applied by the user and to dissipate the energy applied by the user. For example, U.S. Pat. No. 4,822,037 discloses an exercise dynamometer including an electric particle brake having a stator mounted to the frame of the apparatus and a rotor connected to the motion element driven by the user. The control system varies the current supplied to the electric particle brake, thereby varying the drag applied by the brake directly and providing control for the exercise program. U.S. Pat. Nos. 4,261,562; 4,082,267; 3,848,467; 4,822,036; and 4,750,738 all disclose use of a dynamoelectric machine such an electric motor or generator for controlling the speed of the apparatus and dissipating the energy input by the user. U.S. Pat. No. 4,842,274 discloses a variant of this approach in which a hydraulic clutch is interposed between the dynamoelectric machine and the movable element of the apparatus.
Systems which employ dynamoelectric machines capable of operation either as a motor or as a generator provide excellent control of the apparatus. However, apparatus of this nature suffers from a significant disadvantage in that the dynamoelectric machine must have significant power dissipation capacity. This in turn leads to a requirement for a large, heavy and expensive machine.
Accordingly, there are still needs for further improvement in exercise apparatus.